Excitation of Azimuthal Modes in an Axisymmetric Jet
Low order azimuthal modes of jet instability are introduced acoustically using an azimuthal array of speakers. The evolution of axisymmetric and helical instabilities, excited at the frequency of the preferred mode, are mapped along the potential core region. The amplification of the axisymmetric mode is much stronger than the helical mode and the agreement between phase locked measurements and stability predictions is much better. Phase-locked measurements of the helical instability show evidence of resonant interaction with other azimuthal modes.
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